Grid structures are lattice structures that can span over relatively large spaces using little material compared to conventional wall-ceiling or column-beam structures. Grid structures in the form of gridshells have been widely used to construct hangars, domes, and pavilions that require uninterrupted covered space. Gridshells save material by using double-curved surfaces that follow the lines of structural thrust, thereby achieving economical, efficient and elegant structures.
The use of double-curved surfaces, however, also introduces considerable challenges for the design and fabrication of such grid structures. Freeform gridshells tend to produce variable and complex structural joints between load-bearing beams. For example in parabolic or otherwise variable curvature, unique joints are required at every node of the gridshell.
Conventionally, there are several ways of achieving variable curvature in such structures. One of the commonly used methods requires the fabrication of unique angled joints. As shown in FIG. 14, the structural beams may be straight. The curvature of the gridshell is achieved through the use of a large number of uniquely angled joints, for example ball joints, at every node of the gridshell for joining the straight structural beams. Constructing such joints is costly, requires strong materials (e.g. steel), and requires advanced machinery capable of milling customised three-dimensional elements.
Another conventional method requires restricting the grid to a rectangular grid, i.e. subdividing a complex curved form into a grid of X and Y structural axes. As shown in FIG. 15, flat beams follow the axes and connect structurally at intersections. In this method, each flat beam is required to be uniquely cut in accordance with the curvature of the section it is to be fitted. The method is not suitable for line networks composed of irregular n-gons.
In yet another method as shown in FIG. 16, the gridshell is formed from a plurality of long continuous beams. The plurality of long continuous beams are typically connected into a flat grid on the ground, and then gradually erected into shape by pushing in the, supporting edges on site. This requires space and supporting ground, setting constraints on where such structures can be built. The continuity of the members further restricts the kinds of line networks that can be used in this method. For example, the method is not suitable for line networks composed of irregular n-gons. There are also important constraints in the erection of such gridshells.
In another method as shown in FIG. 17, the gridshell curvature is achieved through the use of curved structural beams with uniquely cut edges for joining with other curved structural beams. In this method, the curved structural beams typically require 3D fabrication, which can be costly and restrictive.
A need therefore exists to provide a grid structure which will overcome at least some of the limitations of the above conventional methods.